Energy-saving circuit based on control of a display device of a terminal for mobile communication in dependence on the operating state

ABSTRACT

For a terminal for mobile communication which includes a display device it is proposed to save energy by arranging a control device so as to disconnect at least a part of the display device in dependence on a relevant operating state.

[0001] The invention relates to a terminal for mobile communication, for example a so-called handset or cordless telephone. In such apparatus various energy-saving modes are activated by evaluation of operating states, which energy-saving modes prolong the so-called life of the apparatus which usually utilize a rechargeable power supply source. Therefore, such apparatus are usually equipped with a liquid crystal display having a very low power consumption.

[0002] It is an object of the invention to reduce the power consumption in an apparatus of the kind set forth.

[0003] This object is achieved by taking the steps disclosed in the characterizing part of claim 1.

[0004] Surprisingly it has been found that disconnection of a part of the display device also yields a reduction of the power consumption in liquid crystal displays. Until now such disconnection was considered to be superfluous, because the power consumption of the other parts of a terminal imposes far higher power requirements also in the standby mode. As steps for reducing the power requirements in the standby mode become more and more effective, however, such a power-saving step also has noticeable effects on the standby time.

[0005] Complete disconnection of the display device involves the risk that the user is given the wrong impression that the power supply source in the terminal apparatus is fully exhausted. In a special embodiment, therefore, all parts of the display device are deactivated except for the part showing the name and/or the logo of the mobile radio operator at which the terminal is checked in at the time.

[0006] The decision as to when the terminal apparatus should enter the operating state in which it partly or completely deactivates the display device can in principle be taken in a time-dependent manner, for example by measurement of the time elapsed since the last actuation of a key. Additional sensors, such as a light-sensitive sensor or a motion-sensitive sensor, for example, can switch off the display device completely, for example when the terminal apparatus is present in the dark. In this case a display is fully useless, since a user cannot make out anything without additional backlighting which, as is generally known from the state of the art, can be activated only by actuation of an arbitrary key. A motion-dependent sensor can switch the display device, for example from partial display to full display again. This makes sense, for example, when a terminal rests in an immobile state, for example on a table. Full display is then activated again by touching the terminal.

[0007] The invention will be described in detail hereinafter with reference to an embodiment as shown in the drawing. Therein:

[0008]FIG. 1 shows a display device in which all display sections are activated,

[0009]FIG. 2 shows a display device in a first energy-saving mode in which only a part of the display device is activated, and

[0010]FIG. 3 shows a control device of a terminal according to the invention.

[0011]FIG. 3 shows a control device 6 of a terminal for mobile communication whereto a display device 1 is connected. Two separate sections 2, 3 of the display device can be activated independently of one another by means of control lines. Two sensors, that is, a light-sensitive sensor 7 and a motion-sensitive sensor 8, are connected to the control device 6. In the basic state, for example immediately after the switching on of the terminal, both sections 2, 3 of the display device 1 are activated. FIG. 1 shows a display device 1 in which, for example, the receiving field strength of a mobile radio transmitter received is displayed by means of appropriate first symbols 4 in a first section 2 whereas the charging state of the accumulator is displayed by means of second symbols 5. The name 3 of the mobile radio operator in which the terminal apparatus is checked in is displayed in a second section of the display device 2.

[0012] When the terminal is stored, for example in a handbag by a user, a sudden decrease of the illumination level occurs in the vicinity of the terminal apparatus. On the basis of an evaluation by the light-sensitive sensor 7, the control device 6 recognizes this state and deactivates both sections 2, 3 of the display device 1. For obvious reasons the display device is not shown in this state of operation, because nothing could be seen on the display device.

[0013] When the terminal is removed from the handbag and light is once more incident on the photosensitive sensor 7, the control device 6 activates both sections of the display device again. After a given period of time has elapsed, the display device is partly activated by evaluation by the motion-sensitive sensor 8. FIG. 2 shows this operating state in which only the name of the mobile radio operator can be recognized. This operating state occurs, for example when the terminal is placed on a table.

[0014] As is shown, arbitrary possibilities for activation of the display device 1 can be created by appropriate construction and programming of the control device 6 for different operating states of the terminal and by measurement of the elapsed time and by means of sensors. Just to mention one further application, a distinction can be made not only between ambient light and absence of ambient light, but it is also possible to evaluate the level of the ambient light, so as to switch over to partial display, for example in the case of an intermediate ambient light level as sometimes encountered in pubs. 

1. A terminal for mobile communication which includes a display device, characterized in that a control device (6) is arranged to disconnect at least a part of the display device (1) in dependence on a relevant operating state.
 2. A terminal for mobile communication as claimed in claim 1 , characterized in that at least one sensor element (7) is connected to the control device (6) and that the control device (6) is arranged to evaluate the state of said sensor element (7) in relation to an operating state to be determined.
 3. A terminal for mobile communication as claimed in claim 2 , characterized in that the sensor element (7) is a photosensitive sensor.
 4. A terminal for mobile communication as claimed in claim 2 , characterized in that the sensor element (8) is a motion-sensitive sensor.
 5. A terminal for mobile communication as claimed in claim 1 , 2 , 3 or 4, characterized in that in an operating state only a part of the display device in which the name or the logo of a mobile radio operator is displayed is still activated. 